Experimental Study of Confined Low-, Medium- and High-Strength Concrete Subjected to Concentric Compression

An experimental study of 23 low-, medium- and high-strengthconcrete columns is presented in this paper. Square-confined concrete columns without longitudinal reinforcement were designed, and tested under concentric axial compression. The columns were made of concrete with a compressive strength ranging between 30 MPa and 70 MPa. The test parameters in the study are concrete compressive strengths and confining steel properties, i.e. spacing, volumetric ratios and configurations. The effects of these parameters on the strength and ductility of square-confined concrete were evaluated. Of the specimens tested in this study, the columns made with higher-strength concrete produced less strength enhancement and ductility than those with lower-strength concrete. The steel configurations were found to have an important role in governing the strength and ductility of the confined high-strength concrete. Moreover, several models of strength enhancement for confined concrete available in the literature turned out to be quite accurate in predicting the experimental results

Pengaruh Pemodelan Zona Terkekang Terhadap Prediksi Hubungan Momen-Kurvatur Kolom Persegi Beton Mutu Tinggi

. This paper studies one aspect of confinement modeling of high strength concrete square columns subjected to axially eccentric compression. Confined zone models were studied to evaluate their effect on the analytical prediction of strength and ductility of high strength concrete square columns. Several models of confined zones found in literatures were discussed to observe their characteristics and sensitivity. Based on the findings, a computer program MOKUR2D was developed. In the program, confined zone in reinforced concrete columns can be modeled with three different approaches, i.e. conventional models (using a coefficient of effective confinement), models with unconfined arching zone, or models with three zones of confinement. A comparative study using the program was later carried out on 4 high-strength concrete square columns tested by Sheikh and Bayrak [1998]. The cross-section size of all columns was 305 x 305 mm. All columns were reinforced with 8 bars of 19.5 mm diameter, uniformly distributed around the core perimeter. Yield strength of the rebars was 454 MPa. Two types of ties configuration ties were used with volumetric ratio varying from 1.68 percent to 5.12 percent. The spacing of the ties was from 90 mm to 108 mm. From the study, it was found that the conventional model is able to produce a fairly good estimate of test results. The best estimate of test results is given by the model with three zones of confinement in which the arching zoneis assigned with 50% of full confinement

Pemodelan Retak Pada Struktur Beton Bertulang

. This paper presents a crack model for reinforced concrete structures by using nonlinear finite element method. The crack model used in this study is a discrete crack to simulate strain discontinuity, Discrete cracks are inserted into the structure when the principal tensile stress of nodes have reached the tensile strength of concrete. Insertion of discrete cracks into the structure is only performed when resulting stress combinations are dominated by normal tension stress. Nevertheless, if the principle tension stress on a Gauss point has exceeded the tensile strength of concrete, the craks is treated as a smeared crack with a change in material behavior from one isotropic to another orthotropic character. To find the appropriate direction and pattern of cracks, insertion of discrete cracks into the structure is not only performed by node separation at nodes which have reached the tensile strength of concrete, but also by rotation of the crack perpendicular to the direction of the principle tension stress and dragging the crack-tip node as far as the crack has propagated. Some specimens with different cases e.i Beam J4 (Burns and Siess 1962), Beam OA (Bresler dan Scordelis 1963) and Beam A4 (Ahmad et al. 1986) were analyzed to validate the model. The model is not only able to shows that the structure response is very close to the experimental test, but also can describe the proper crack pattern

Confinement of Reinforced-Concrete Columns with NonCode Compliant Confining Reinforcement Plus Supplemental Pen-Binder

. One of the important requirements for earthquake resistant building related to confinement is the use of seismic hooks in the hoop or confining reinforcement of reinforced-concrete column elements. However, installation of a confining reinforcement with a 135-degree hook is not easy. Therefore, in practice, many construction workers apply a confining reinforcement with a 90-degree hook (non-code compliant). Based on research and records of recent earthquakes in Indonesia, the use of a non-code compliant confining reinforcement for concrete columns produces structures with poor seismic performance. This paper presents a study that introduces an additional element that is expected to improve the effectiveness of concrete columns confined with a non-code compliant confining reinforcement. The additional element, named a pen-binder, is used to keep the non-code compliant confining reinforcement in place. The effectiveness of this element under pure axial concentric loading was investigatedcomprehensively.The specimens tested in this study were 18 concrete columns,with a cross-section of 170 mm x 170 mm and a height of 480 mm. The main test variables were the material type of the pen-binder, the angle of the hook, and the confining reinforcement configuration.The test results indicate that adding pen -binders can effectively improve the strength and ductility of the column specimens confined with a non-code compliant confining reinforcement

Kinerja Struktur Portal Terbuka Beton Bertulang Terhadap Beban Lateral

Kejadian gempa bumi telah banyak menyebabkan runtuhnya dan robohnya bangunan beton bertulang terutama rumah dan gedung. Salah satu penyebabnya adalah banyaknya bangunandibawah tujuh lantai termasuk rumah di bangun tanpa mengikuti peraturan yang ada. Sehingga pada saat gempa terjadi, bangunan tersebut mengalami kerusakan. Penelitian ini akan mencakup aspek pengujian dan analitis. Uji eksperimental dilakukan pada satu portal terbuka yang memiliki satu bentang dan satu tingkat dengan skala model setengah. Kerusakan yang terjadi berupa retak lentur, geser dan rompal pada beton kolom dan sambungan balok kolom. Kerusakan akibat beban lateral diperbaiki dan diuji kembali terhadap beban lateral. Perbaikan portal dilakukan hanya padabeton yang rusak akibat beban lateral. Pembebanan yang diaplikasikan adalah dalam bentuk beban lateral siklik sebagai simulasi beban gempa. Tujuan dari eksperimen ini diharapkan bisa diperoleh kinerja portal beton bertulang sebelum mengalami kerusakan (portal terbuka/portal utuh) danportal setelah mengalami kerusakan kemudian diperbaiki (portal perbaikan). Dari analisis hasil pengujian, diperoleh kapasitas lateral portal utuh dan portal perbaikan relatif sama. Tetapi, kekakuan dan kemampuan mendisipasi energi serta daktilitas portal utuh lebih besar dibandingkan portal perbaikan. Hal ini menunjukan bahwa kinerja portal utuh tetap lebih baik dibandingkan portal perbaikan

Kontribusi Bubuk Slag Nikel Di Dalam Meminimalkan Dampak Intrusi Mikroorganisme Terhadap Perilaku Fisik Material Beton

. This paper is presents the experimental study on use of nickel slag powder in the minimization intrusion impact of microorganism to physical properties of concrete materials. The intrusion of microorganism into concrete pores is fungus (Aspegillus Niger) and yeast (Sacchromycodes ludwigi) groups. Both types of this microorganism produce organic matter is acetate acid (CH3COOH) able to react with chemical compound in concrete materials, especially calcium hydroxide and calcium silicate hydrate compound. The reaction affect on the increasing of porosity, permeability coefficient, and loss masses of concrete. The effect of intrusion of microorganism can be minimized by use 16% nickel slag powder. For concrete without nickel slag powder, physical properties tend to follow equation of geometry function (power equation equation), while the concrete of 16% nickel slag powder as indicated by equation of saturated growth rate function

Optimisasi Bubuk Slag Nikel Dengan Sistem Ternary C-A-S

. This papers study concerning optimization of nickel slag powder as substitution material to partial cement by C-A-S (CaO-Al2O3-SiO2) ternary system. Optimization conducted to determine procentage of nickel slag powder in the consuming calcium hydroxide compound as hydration product of tricalcium silicate (C3S) and dicalcium silicate (C2S) cement with water so that form secondary of calcium silicate hydrate (CSH) compound. By the phase diagram C-A-S ternary system, procentage of optimum nickel slag powder determined by intersection point between of balance line pozzolanic reaction and mixing line of material cement and nickel slag powder. Analysis result indicate that by approach of C-A-S ternary system, percentage optimum of nickel slag powder is 14,59%

Studi Eksperimental Perilaku Hubungan Pelat-Kolom Terhadap Kombinasi Beban Gravitasi Dan Lateral Siklis

. Flat slab structures are widely used for buildings because of its advantages both in structural and architectural aspects. Besides its advantages, there is a weakness leads to a poor structural behavior under combined gravity and lateral load. The weakness is concentrated in slab-column connections, where flexural and shear stresses are accumulated as a resultant of gravity load and unbalanced moment caused by lateral load such as earthquake. To solve the problem, especially in potential earthquake zone such as most of the Indonesia region, it is necessary to conduct researches to improve slab-column connections behavior. This paper reports the result of research conducted using three specimens of half scaled interior slab-column connection sub-assemblages designed using simillar dimensions, materials, and details, except the shear reinforcement details. The first specimen, constructed as a control specimen, used standard stud rails designed to comply with ACI codes. The second and third specimens used modified stud rail details. All specimens were subjected to a constant gravity load simulated by concrete blocks and cyclic lateral displacements ranging from elastic to inelastic responses. The experimental results show that modification of the stud rails significantly improves the specimen behavior especially the stiffness and energy dissipation

The Hysteretic Behavior of Partially Pre-Stressed Beam-Column Joint Sub-assemblages Made of Reactive Powder Concrete

Reactive powder concrete (RPC) is an alternative to normal concrete (NC) allowing for significantly higher strength of partially pre-stressed concrete structures. In the Indonesian national standard SNI 03-2847-2013 (2013) and the American standard ACI 318-14 (2014), the partial pre-stressed ratio (PPR) is limited to a maximum of 25.0 percent to ensure that pre-stressed concrete structures remain ductile and capable to dissipate seismic energy sufficiently. The objective of this experimental study was to investigate the hysteretic performance of partially pre-stressed-RPC (PP-RPC) for both interior and exterior beam-column joint sub-assemblages. Four specimens with different levels of PPR were tested with a combination of constant axial compression and cyclic lateral loads. The PPR used for the first and the second two specimens were 22.8% and 33.8%, respectively. The strength of the RPC was 101.60 MPa for all specimens. The results showed that increasing the PPR of PP-RPC improves its hysteretic performance. The best performing specimen, with a PPR of 33.8%, had a ductility that was 1.97 times that of the specimen with a PPR of 22.8%